.btn-expand {
  max-width: 16px;
  box-sizing: content-box;
  color: rgba(0, 0, 0, 0);
  transition: max-width .2s ease;
}
.btn-expand.btn-xs {
  max-width: 12px;
}
.btn-expand.btn-sm {
  max-width: 14px;
}
.btn-expand.btn-lg {
  max-width: 18px;
}
.btn-expand i {
  color: #333;
}
.btn-expand.btn-link i {
  color: #428bca;
}
.btn-expand.btn-primary i,
.btn-expand.btn-success i,
.btn-expand.btn-info i,
.btn-expand.btn-warning i,
.btn-expand.btn-danger i {
  color: #fff;
}
.btn-expand:hover,
.btn-expand:focus,
.btn-expand:active {
  max-width: 400px;
  transition-duration: .5s;
}